Vodafone currently have a Free SIM Offer going. You can obtain a Free Vodaphone SIM in Standard SIM
Micro SIM or Nano SIM format. They have various packages you can opt to subscribe to such as Freedom Freebee, Freedom Minutes, Freedom Data & Freedom Text.
All you have to do is enter your details on the following site.To Get A Vodafone - Free SIM Click Here

There's no time limit on if your with Three's network or just own a Three handset, You could have bought your device today, or several years ago. If it is locked to 3, they will unlock it for you free of charge.

Three will be upgrading and offering 4G data free to their 3G customers, read on for what Three says.

In December, London, Birmingham and Manchester will see the start of our 4G roll out. That’s not a bad early Christmas present is it? Even better than that, we’ll be busy rolling out in a further 50 cities by the end of 2014.